The Climate Science Approach in Floodplain ManagementKristina Murphy, EIT, CFM

The Association of State Floodplain Managers Conference May 2, 2017

Overview

Climate science and climate resilience are terms that have recently appeared in floodplain management. The

Biggert-Waters Reform Act to the National Flood Insurance Program (NFIP) states that climate change science should

be considered in floodplain mapping. The Federal Flood Risk Management Standard (FFRMS) states that a climate-

informed science approach (CISA) is the preferred method for establishing flood hazard areas.

•

• What elements are required to address concerning changes in climate?

• What is the climate science approach and what are the benefits?

• What background information should floodplain managers be aware of concerning changes in climate?

• What are the projected effects and impacts to flood risk from changes in climate?

• What are the challenges and solutions to implement the approach?

Specific examples for floodplain and stormwater management will be given for coastal regions, drought and

fire prone regions, and areas subject to increased rainfall.

Introduction

• Directly west of

Chicago

• 42 municipalities

• 336 square miles

• 916,924 residents

(2010 census)

• Elevations range from

982 to 590 feet MSL

• 38 inches average

annual precipitation

• Stormwater

management and

floodplain ordinance

adopted in 1991

• 16 flood control

facilities with almost 4

billion gallons total

capacity

ChicagoDuPage County, Illinois

Introduction

August 1987

$220 million

July 1996

$600+ million

September 2008

$155 million

July 2010

$300+ million

April 2013

$372 million

*=state record

Northeastern Illinois Rainfall Events and Associated Damages

Nationwide, the 30-year average losses due to flooding are $7.96 billion.

Federal Initiatives

FEMA Climate Change Policy

Federal Emergency Management Agency (FEMA) - Climate Change Adaptation Policy Statement (2012)www.fema.gov/climate-change

• Challenges posed by climate change:

o More intense storms

o Frequent heavy precipitation

o Heat waves

o Drought

o Extreme flooding

o Higher sea levels

•

o Impacts on mitigation, preparedness, response, and recovery operations

o Resiliency of critical infrastructure and various emergency assets

o Climate change could trigger indirect impacts that increase mission risks

www.fema.gov/media-library-data/20130726-1919-25045-6267/signed_climate_change_policy_statement.pdf

FEMA Climate Change Policy

policies, and operations:1. Establish partnerships with other agencies and organizations that possess climate science and climate change adaptation

expertise.

2. Continue to study the impacts of climate change on the National Flood Insurance Program (NFIP) and incorporate climate change considerations in the NFIP reform effort.

3. Evaluate how climate change considerations can be incorporated into grant investment strategies with specific focus on infrastructure; evaluate methodologies or tools such as benefit/cost analysis.

4. Understand how climate change will impact local communities and engage them in addressing those impacts.

5. Promote building standards and practices, both within FEMA programs and in general, that consider the future impacts of climate change.

6. Evaluate the potential impact of climate change may have on existing risk data and the corresponding implications for Threat Hazard Identification Risk Assessment (THIRA) development and operational planning.

7. Continue to pursue a flexible, scalable, well equipped, and well trained workforce that is educated about the potential impacts of climate change.

Biggert-Waters Act

The Biggert-Waters Reform Act of 2012• Requires a Technical Mapping Advisory Council (TMAC) to issue guidance on how to incorporate best

available climate science into flood insurance rate maps.

• Requires TMAC to develop recommendations for future conditions mapping, including impacts of sea level

rise and future development on flood risk.

• Detailed specific scientific considerations should be included when updating flood risk maps, including

any relevant information on:

o coastal inundation and storm surge modeling;

o stream flows, watershed characteristics, and topography;

o land subsidence, coastal erosion areas, and changing lake levels; and

o best available science regarding future changes in sea level rise, precipitation, and hurricane intensity.

Federal Flood Risk Management Standard

The Federal Flood Risk Management Standard (FFRMS) issued in 2015 will require any construction funded by

federal money, including disaster relief grants, to meet the specified standards.

When complying with this Executive Order (13690), the floodplain shall be established using one of the

following approaches:

• Climate Informed Science Approach The elevation and flood hazard area that result from using a climate-

informed science approach that uses the best-available, actionable hydrologic and hydraulic data and

methods that integrate current and future changes in flooding based on climate science. For critical

actions, the elevation determined must be higher than the elevation under the freeboard value approach.

• Freeboard Value Approach; or

• 500- Elevation Approach

Guidelines released October 8, 2015 state that the Climate Informed Science Approach is preferred.

The Climate Science Approach

The Approach

Engineers use historic data for designing infrastructure

expected to persist for 20 to 50 years in the future.

Past records do not contain all the possibilities of

extremes and trends of the future.

The climate science approach uses available climate

model output to assist with predicting future trends for

planning and design.

Benefits of the Approach

• The climate science approach supports adaptation and

mitigation, which reduces vulnerability and increases

resilience to extreme and/or more frequent events.

• Build better rather than repeatedly rebuild.

• Resilience: the ability to adapt to changing conditions and

rapidly recover from disruptions.

• Adapt: change to be better suited for the environmental

conditions.

• Mitigate: actions to improve resilience and reduce

vulnerabilities to future risks.

Adapt

Resilience Strategies

Mitigate

Benefits of the Approach

• Limit property and infrastructure damages

• Limit economic losses

• Increase public safety, avoid casualties

• Avoid loss of essential services (utilities)

• Avoid loss of function of critical facilities and roads

o Displacements, disruptions

o Road closures, detours

• Prepare for emergency response (evacuations, rescues)

• Reduce costs to repair or rebuild from more frequent and/or extreme

events

• Responsible spending of tax payer money

One large event can result in

total loss of use.

Climate Science Background

Background

Average temperature increase of 2oC is predicted by 2065.

2oC warmer atmosphere can hold 14% more water vapor.

Climate is the average of weather at a

particular location. Large or abrupt shifts

in frequency of extreme events are of

concern.

National Climate

Assessment (NCA) –

2014

http://nca2014.global

change.gov

Background

Consequences from changes in

climate to flooding:

• Increased precipitation

• Decreased precipitation

• Sea level rise

• Snowpack

Background

Projected overall

changes increase

exponentially for

the heaviest

precipitation and

slightly decrease

for the lightest

precipitation.“Very heavy” defined as the heaviest 1%

of all daily events.

Background

Seasonal precipitation change projections for 2071-2099 compared to 1970-1999

Projections for 2041-2070 compared to 1971-2000 for CMIP3 A2 emissions scenario

Climate Data Sources

• U.S. Bureau of Reclamation’s Downscaled CMIP3 and CMIP5 Climate and Hydrology Projections (DCHP) o 30 different models available

http://gdo-dcp.ucllnl.org/downscaled_cmip_projections/

o Federal Highway Administration data extraction and processing tool www.fhwa.dot.gov/environment/sustainability/resilience/tools/

• North American Regional Climate Change Assessment Program (NARCCAP)www.narccap.ucar.edu

CMIP = Coupled Model Intercomparison Project Phase #

Climate Data Sources

• National Center for Atmospheric Research (NCAR) Community Climate System Model (CCSM) in Geographic Information System (GIS) formats

• http://gisclimatechange.ucar.edu/

• USGS National Climate Change Viewer (NCCV)https://www2.usgs.gov/climate_landuse/clu_rd/nccv.asp

• Sea Level Rise Trends http://tidesandcurrents.noaa.gov/sltrends.sltrends.html

• Sea Level Rise and Coastal Flooding Impacts Viewer https://coast.noaa.gov/slr/

Impacts from Changes in Climateto Floodplain and Stormwater Management

Increased Precipitation

http://www.isws.illinois.edu/pubs/pubdetail.asp?CallNumber=ISWS+CR+2016-05

Increased Precipitation

Climate model emissions scenarios:

A1B: rapid economic growth followed by a decline after 2050 due to new and more efficient technologies; balance across fossil and non-fossil energy sources

A2: regionally oriented economic development and slower economic growth

B1: rapid transition to clean and efficient energy technologies (i.e. solar, wind); low emissions

Time periods modeled:

• - hindcast (1961 2000)

• 2046 2065 [2050] 34 years into the future

• 2081 2100 [2090] 74 years into the future

Increased Precipitation

Today’s 25-year storm will be the

15-year in 2050 and

10-year in 2090.

Increased Precipitation

3.0

4.0

5.0

6.0

7.0

8.0

9.0

0 10 20 30 40 50 60 70 80 90 100

Bulletin 70(1961-1989)

A1B: 2046-2065

A1B: 2081-2100

A2: 2046-2065

A2: 2081-2100

B1: 2046-2065

B1: 2081-2100

Precipitation Comparisons at Wheaton

Return Period (years)

Pre

cip

itat

ion

(in

ches

)

Impacts to Flood Control

DuPage River Feasibility Study

• Total watershed area 378 sq. mi.

o East and West Branches of the DuPage River

• Federal sponsored project U.S. Army Corps of Engineers

o Requires future precipitation data is utilized

o If the plan is approved by Congress, eligible for 65% federal funding for

flood control projects (storage, levees, non-structural)

• Existing conditions is year 2020, future conditions is 2040

Impacts to Floodplains

Every watershed will

have unique responses

to changes in

precipitation,

depending upon:

• location in watershed,

• channel and structure

hydraulics, and

• overbank topography.

Impacts to Floodplains

(June 2013)

considered changes to precipitation, land use, and sea level

rise.

By 2100, the 1% annual chance (100-year) floodplain depth and

lateral size is projected to increase, on average, by 45% above

current levels across the nation.

• About 30% of these increases in floodplain area and

flood depth may be attributed to normal population

growth (i.e. land use) while the remaining 70%

represents the influence of climate change.

By 2100, the population within riverine and coastal floodplains

will increase by 130-155%.

• The total number of policyholders participating in the

NFIP may increase approximately 80-100%.

• The average premium per policy will increase by

about 10-70%.

www.aecom.com/deployedfiles/Internet/News/Sustainability/FEMA%20Climate%20Change%20Report/Climate_Change_Report_AECOM_2013-06-11.pdf

Source: EPA CIRA

Impacts to Stormwater Management

• Cost benefit analysis of increased protection

o Evaluate flood control projects

over the entire design life

• Plan and budget for future retrofits

o Estimate number of future

high risk structure or

repetitive loss acquisitions

o Mitigation projects

• Future precipitation + Future land use Future flows Future floodplains

o Elevate critical buildings (hospitals, wastewater treatment plants)

o Elevate critical roads; size culverts and bridges to withstand future extreme events

o Reduce and limit erosion and property and infrastructure damages

o Evaluate open space preservation, set-backs, and freeboard requirements

o Avoid development / redevelopment in future high-risk areas

o Avoid putting properties “into” the Special Flood Hazard Area (SFHA) when

updating modeling and mapping; reduce grand-fathering subsidies

• Future precipitation + Future land use Future flows Future stormwater utilities

o Account for future increases to the design storm

o Size storm sewers, ditches, and culverts/bridges to meet design life flows

o Pipe outlet (tail-water) considerations

o Pipe surcharging in known problem areas

Coastal Impacts

• Thermal expansion of water and

melting ice causes sea level to rise;

coupled with land subsidence

• Nuisance flooding from high tides

and storm surge of higher seas, as

well as storm sewer and river

flooding from submergence of

outlets

• FEMA Zones VE and V (1-30) may

shift inland and increase vertically

• Cost of solutions (flood walls, new

sewers, elevating, floodproofing,

relocation) are expensive

Drought Impacts

• Drought is a prolonged

period of abnormally low

rainfall and/or lack of soil

moisture

• Drought contributes to

flooding through increased

risk of wildfires

o Dry periods stress trees

o Pests can kill stressed trees

o Longer warm periods allow

pests to grow larger and

live longer

Wildfire Impacts

Wildfires prior to extreme rain events

cause greater flooding impacts.

• Dead wood creates fuel for wildfires

• Wildfires kill water absorbing vegetation

and changes the soil composition

• Burn scars create increased acceleration of

runoff because there is no vegetation to

slow down the water, especially in steep

terrain

•

in greater flow volumes (hydrology

changes!)

Wildfire Impacts

Wildfires prior to extreme rain events cause

greater flood damages.

• Increased risk of ash and mud flows;

landslides

• Dead trees can become mobile

• Woody debris and eroded soil can clog and

destroy culverts and bridges, creating

additional flooding damages

Snowpack Impacts

• Changes to snowpack:

o Decreases to snowpack because warmer temperatures causes

precipitation to fall as rain instead of snow

o Earlier springtime melting of snowpack due to warm temperatures

occurring earlier

• Impacts from changes:

o Shifts to peak runoff timing, may coincide with spring rain

o Management of dual use flood control / water supply reservoirs

Challenges to the Approach

Challenges and Solutions

• Challenges of the Climate Science Approach:

o Lack of easy-to-use data available

o Lack of acceptable data by permitting agencies

o Lack of local support or belief in climate science

• Solutions to the Challenges:

o Encourage agencies to fund studies to provide applicable datasets

o Encourage permitting agencies to establish which datasets to use

o

o

o Creating resiliency to damages from frequent and extreme events

o Cost benefit analysis to justify building better vs. rebuilding repeatedly

o Useful words: adaptation, mitigation, resilient, factor of safety, future

trends, sustainable, and risk reduction

Recommendations

• Climate models are the best available information that we have to assess

future condition trends.

• The impacts of changes in climate will vary depending upon the location. One

solution will not fit all.

• Consider future conditions to ensure the design life is met, especially for

critical infrastructure and known problem areas.

• Use future conditions precipitation with future conditions land use in

hydrologic and hydraulic models to determine future floodplains to:

o Preserve floodplains;

o Reduce and limit property and infrastructure damages;

o Reduce flood insurance premiums;

o

o Reduce the need for grand-fathering and future buy-outs.

• Keep the big picture in mind. Focus on low regret and low cost options.

Contact Information

Kristina.Murphy@DuPageCo.org

(630) 407-6821

“Knowing is not enough; we must apply. Willing is not enough; we must do.” -- Goethe